3rd Generation Partnership Project, Release 99 (3GPP R99) defines an end-to-end congestion control mechanism based on 3GPP Quality of Service (QoS) profile handling. The 3GPP QoS profile typically comprise two parameters, the Traffic class and the Traffic Handling Priority (THP), which are used by a Radio Access Network (RAN) Scheduler in order to set traffic priority in a congestion situation. There are four possible values for Traffic Class (called Conversational, Streaming, Interactive and Background), and three values for the THP (only applicable to Traffic Class Interactive).
Policy and Charging Control (PCC) in the Internet Protocol Multimedia Subsystem (IMS) and similar service network architectures involves network elements such as a Charging Rules Function (PCRF) and a Policy Charging Enforcement Function (PCEF). The PCRF provides a set of traffic filters for policy control and flow based charging, and communicates with Application Functions (AFs) to determine authorized resources for session-based services. The PCEF, on the other hand, provides service data flow detection, policy enforcement and flow based charging functionalities.
In the PCC framework (e.g., according to 3GPP Release 7), the PCRF has the capability of providing one specific QoS profile at bearer establishment/update, which is enforced backwards towards the RAN. If congestion happens, the RAN may take into account the Traffic Class and/or THP value in order to decide which bearers are assigned a higher priority and, consequently, more bandwidth resources.
Further, 3GPP Release 8 has defined another QoS control mechanism, which is based on admission control and resource reservation principles: provide different congestion treatment for different kinds of subscribers, and guarantee a specific QoS for specific services even in the case of congestion (and therefore not allowing in a congestion case the establishment of services requiring a high QoS). For this purpose, the QoS control mechanism defined in 3GPP Release 8 distinguishes two different kinds of bearers: Guaranteed Bit Rate (GBR) and non-GBR. Besides, 3GPP Release 8 has introduced another way of handling priority: the QoS Class Identifier (QCI). The QCI is a number, preconfigured by the operator, which number implies a certain meaning regarding parameters for packet forwarding treatment. Each service can have one or more related QCIs. In addition, every QCI (GBR and non-GBR) is associated with a priority level. The QCI mechanism enables a service-specific congestion control, providing different values for different services running on the same bearer. The PCRF can provide a specific QCI value for example at bearer establishment/modification.
Congestion control mechanisms based on QoS profile (Traffic Class and THP) and QCI are applied in a ‘pre-configured’ way. That is, the mechanisms are assigned at bearer activation/update, and are applied only in case congestion happens. The mechanisms work on a scheduling basis, assigning resources to the most prioritized bearers/services, but do not depend on the actual cell congestion, and can therefore not react to the congestion situation dynamically, for example, to enable the removal of the congestion situation as quickly as possible. In fact, the above mechanisms may even permit a permanent congestion situation.
Regarding the 3GPP QoS profile congestion control mechanism, this mechanism applies to the bearer as a whole. Therefore, the network is not capable of a service-specific control (e.g., is not able to apply a throughput limitation just to one specific service of all the services running on a specific bearer). Besides, 3GPP Release 8 requires the initial bearer activation support on side of the network, which implies requirements in the terminals (for example, legacy terminals are not supported).